The present invention is directed to an implantable inductively programmable temperature sensing transponder, and, more particularly, to a transponder having operations which may be modified through software control
Implantable programmable temperature transponders are passive devices that are implanted under the skin of laboratory animals, by way of example, for positive animal identification. As is known in the art, conventional transponders, such as those sold by Bio Medic Data Systems, Inc. include a coil antenna coupled to an integrated circuit (IC) chip. The chip includes a memory and a thermistor. Circuitry is provided for receiving an interrogation signal, deriving power from the interrogation signal, deriving timing clocks from the interrogation signal, and controlling the memory and the thermistor to output data stored in the memory or temperature information sensed by the thermistor to the interrogator. It is also known in the art to program input data to the on-board memory of the transponder.
This prior art transponder has been satisfactory. However, it suffers from the disadvantage that the integrated circuitry required too much power for operation in the READ MODE. This resulted in the reduced read distance between the transponder and interrogator. The memory, which included an EEPROM was too small and the temperature data was required to be transmitted over the top of sixteen of the memory bits making them unusable. Although the prior art taught locking the data in the memory to preserve the integrity of the memory, the lock was permanent and could not be selectively changed by the transponder user as needed. Furthermore, in the prior art, synchronization between the transponder and interrogator has been performed utilizing a preamble of the transponder's data signal. Because the entire data signal was required to be transmitted as well as the preamble during any synchronization process, time was wasted, slowing down the overall programming and/or read cycle. Furthermore, a single temperature reading taken by the transponder was sent to the interrogator and used as the temperature. Many factors can affect the reading and recording of temperature in a transponder so that there would be fluctuations between successive temperature readings. In effect, a floating temperature value would occur reducing the precision of the temperature read. Lastly, during programming, utilizing conventional signal encoding techniques, the timing of the signal transmitted between the transponder and interrogator was critical. However, because timing was so critical, noise or other environmental factors could readily disrupt the signal, damaging the results.
Accordingly, an implantable programmable temperature transponder which overcomes the shortcomings of the prior art is desired.